Physics Quiz 4

What is a force?  Define in Physics terms

way for us to describe an interaction between two objects.

Magnitude

how weak or strong the force is

Direction

the direction in which the force acts

Any quantity that has both a magnitude (size) and direction

vector

Any quantity that has a magnitude (size) only.

scalar

What is the preferred scientific (SI) unit for force?

Newtons

Newtons abbriviated

N

Normal Force

Occurs when two surfaces are in contact and squish against each other

Direction is always perpendicular (normal) to the surfaces.

Frictional Force

Occurs when two surfaces try to slide past one another.

Direction is always parallel to the surfaces, but in the opposite direction of motion.

Tension Force

Occurs when a rope, cable, or similar is pulled taut (no slack)

Direction is always away from the thing being pulled, in direction of the rope.

Gravitational Force

Occurs when an object with mass is near something like a planet

Direction is always towards the center of the planet.

Fg =

mg

g =

9\.8 N/kg

What does Newton’s first law tell us about the motion of objects that are experiencing balanced forces?

If an object experiences balanced forces (all the forces in all directions add to 0), its motion will not change.
Conversely, if it experiences unbalanced forces its motion MUST change.

Mass

Measure of the amount of matter an object has.

Weight

Measure of the pull of Earth’s gravity on an object’s mass.

Free Body Diagram of sliding box